The present invention relates to improvements in machine tools of the type adapted to automatically perform operations such as boring, milling, facing, turning, grinding or the like, on workpieces, on a production run basis. A machine of the general character with which the invention may be employed is disclosed in the present assignee's U.S. Pat. No. 3,203,316, issued Aug. 31, 1965. Machine tools of this character are required to perform machining operations with ever-increasing precision.
In the patent mentioned, the movement of the slides and tappets is controlled by cams which permit a compound movement of each tool in response to the contours of a cam for the vertical slides, and a separate cam for the horizontal slides which they carry.
To provide even greater versatility and precision, the present machines have been altered to replace the cams with computer numerically controlled (CNC) servo motors and we have determined that this necessitates new structure in the motion transmission system to achieve the accuracy which is required, while still retaining the high production which is necessary. Because, with such structures, the drive is now a rotary motion, which must be positively translated without any lost motion, or rotary looseness, to straight line motion of a tappet operating a bell crank controlled cross slide, it is necessary to avoid the introduction of any linear error due to rotary looseness or radial thrust.
One of the prime objects of the present invention is to provide a mechanism which permits conversion of the control of the x and y axis slides from cam and cam follower control to off-axis, bi-directional NC control, without any loss of precision and introduction of linear error.
Still another object of the invention is to design a construction providing straight line precision movement with a "running fit".
Still a further object of the invention is to provide gravity counterbalancing mechanisms for the slide mechanism which reduces the forces which otherwise would severely stress the motion transmission mechanism.